The present invention is related to the field of systems for feeding and monitoring laboratory animals.
Most biological values measured in laboratory animals respond to qualitative and quantitative variations in food intake. Therefore, methods to assess and vary food quality and quantity are important to all biological researchers, especially to nutrition biologists.
Techniques to assay and change the nutrient quality of lab animal feeds are well established and practiced; however, current methods to measure food intake and feed restrict lab animals are limited and crude.
The common method for measuring food intake of laboratory animals is manual. By this method, a technician loads food into a hopper and weighs the food and hopper at a beginning time. At the end of an interval, the technician again weighs the food and hopper. Food removed over this period is calculated by the difference in weight. Because existing food hoppers are not spill proof, food removed does not necessarily equal food consumed, and correction must be made for food removed but not eaten. Often, removed food falls to the tray where feces and urine collect. To determine how much food was spilled, the technician must meticulously separate the food from solid waste, weigh the spilled food and estimate a correction factor to compensate for the amount of urine that has been absorbed by the dry food.
Thus, this manual method is limited by how often the technician can perform these activities. Also, because these activities require handling of food and (usually) the animal, they are likely to disturb the animal""s feeding behavior, often starting meals of resting animals, or stopping meals of feeding animals. Because of these factors, food intake measurements are usually performed only once or twice weekly, or at most, once or twice daily. Thus, not only are food intake data inaccurate, they also do not allow resolution of 24 hour, diurnal, patterns of food intake.
Two types of partly automated food intake monitoring systems exist. Both require moving animals to specialty housing. In the first, food cups are placed on standard electronic balances, and animals eat from these cups through holes in the bottom of their cage. The gross weight of the food cup is recorded at specified intervals. These weighings can be made often and without disturbing the animals. However, like the manual method, this method does not prevent spillage of food, or fouling of food with urine and feces, thus measuring false increases and decreases in food intake. In addition separating food intake data from the recorded weighings is complicated by the possibility that weighings are changed by the animal touching the food cup at the moment of recording.
In the second method, food is provided as tablets of known weight. Tablets are dispensed when an animal xe2x80x9crequestsxe2x80x9d them by learned behavior such as bar pressing, or by feedback when a tablet receptacle is determined to be empty following removal of the last tablet by the animal. Food intake is determined from the number of tablets dispensed. As previously, this method does not limit food spillage. Also, it can not differentiate between food intake and simple food hoarding. Also, the animal""s diet is limited to materials that can be tableted, thus intake of high fat foods, which can not be tableted, can not be measured by this method.
The above methods determine food intake of animals presented food when unrestricted by time or amount, that is, when allowed ad libitum access to food. However, biologists often want to restrict food intake by amount or time or both. Meal feeding access is limitation of food intake by time alone. Manually, meal feeding is accomplished by simple presentation or removal of food following a schedule. Like the methods described above, meal feeding is laborious, and the presence of the technician may again introduce changes in behavior.
To restrict food by amount, technicians weigh daily amounts of food less than what the animal would consume ad libitum and offer it to the animal once a day. Animals thus restricted, usually consume the smaller amount of food quickly and then fast for the time remaining till the next feeding. This virtual meal feeding complicates the effects of food restriction This effect can be minimized by splitting the restricted amount into several feedings per day. But this introduces more technician labor and interference with animals behavior.
Our patent describes a system consisting of: (1) a spill proof food hopper, which does not limit or interfere with the natural food intake of ad libitum fed animals; (2) a hardware and software system to continuously monitor the weight of this hopper, detecting and recording the time, duration and amount of each meal; (3) a gate system to restrict food intake by time, amount, or both; and (4) a means to do this for one, tens or hundreds of animals coincidentally.
To date, no system exists to control gate opening and closing not simply by time, but by time and amount, thus allowing access to food at a prescribed time for a prescribed time period or until a prescribed amount of food is consumed.
One aspect of the present invention is an animal feeder, comprising a hopper for storing pieces of food. A bottom portion of the hopper has a first opening which is accessible by an animal. The first opening is smaller than one of the pieces of food, but large enough for the animal to gnaw the food through the first opening. The hopper has a receiving surface adjacent to the first opening. The receiving surface is positioned to receive fallen gnawed food and hold the fallen gnawed food in a position accessible by the animal for eating. The hopper is seated on a mounting bracket. The mounting bracket is directly attachable to a container in which the animal is housed.
Another aspect of the invention is a bottom mounting surface attached to the hopper. The bottom mounting surface is removably seated on a self-centering mount. The self-centering mount allows freedom of movement and freedom of rotation by the hopper within a set of predetermined limits. The bottom mounting surface returns to a centered position after a movement or rotation, by operation of gravity.
Another aspect of the invention is a self-centering mount that transmits a downward force from the hopper to a measuring device. The self-centering mount does not transmit an upward force or moment from the hopper to the measuring device.
Another aspect of the invention is a system, method and computer program for calculating an amount of food consumed by an animal. A force applied to a food hopper is measured, and an output signal representing the force is provided. An average weight of the hopper is calculated based on the output signal, and a statistical measure of the output signal other than the average weight is calculated. A beginning and an end of a feeding are identified based on the statistical measure. An amount of the food consumed by the animal during the feeding is calculated based on the average weight before the beginning of the feeding and the average weight after the end of the feeding.
Still another aspect of the invention is a system for controlling feeding of a plurality of animals, comprising a plurality of animal feeders. Each feeder has a respective gate. Each gate has an open position and a closed position, such that a respective animal can access food from a respective feeder when the gate of that feeder is open, and the respective animal cannot access food from a respective feeder when the gate of that feeder is closed. A processor having an embedded CPU determines an amount of food removed from each respective feeder by the respective animal that has access to that feeder. A plurality of actuators automatically open and close each gate in response to control signals. The processor has means for receiving a signal indicating that either a first operating mode, a second operating mode, or a third operating mode is selected. The processor generates and transmits the control signals to each of the plurality of actuators so as to provide access to each animal for a common length of time, if the first operating mode is selected. The processor generates and transmits the control signals to each of the plurality of actuators so as to provide food access to each animal until a common amount of food is removed from each feeder, if the second operating mode is selected. The processor generates and transmits the control signals to each of the plurality of actuators so as to provide food access to each animal until either a common length of time passes or a common amount of food is removed from each feeder, whichever occurs first, if the third operating mode is selected.
Another aspect of the invention is an animal monitoring system comprising a plurality of cage controllers. Each cage controller has a respective processor and a storage device coupled to the processor. Each cage controller receives and stores sensor data from a sensor that collects sensor data from a respective animal specimen. Each cage controller calculates statistics from the sensor data. Each of the plurality of cage controllers is coupled to a local host computer. The local host computer is capable of issuing commands to each of the cage controllers to control collection of the sensor data.
These and other aspects of the invention are described below with reference to the exemplary embodiments.